From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98045][LOW] bpf: Mark faultable stack helpers as sleepable [ Upstream Date: Fri, 25 Sep 2026 07:21:12 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98045 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 44b8d370f2725bad215da3e67668e98ba96671bd List-Id: CVE: CVE-2026-98045 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: bpf: Mark faultable stack helpers as sleepable [ Upstream Commit: 44b8d370f2725bad215da3e67668e98ba96671bd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44b8d370f2725bad215da3e67668e98ba96671bd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98045 Analysis date: Fri, 25 Sep 2026 07:21:12 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98045 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98045 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98045 LOW https://www.kernelcve.org/list/?q=CVE-2026-98045 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;**CWE-400;CWE-703;BEST CVSS score: '4.7';DESCR 'Faultable BPF stack helpers may perform filesystem reads while resolving user space build IDs. The helpers were not marked sleepable, so the BPF verifier could allow them in RCU, preemption disabled, or timer callback contexts where blocking is unsafe. This can result in sleeping in atomic context warnings, lockups, or kernel denial of service. For the CVSS the PR:L is used because triggering normally requires the ability to load and attach a BPF program with delegated BPF related capabilities, rather than full administrative control. The issue is not directly network reachable. No memory corruption, information disclosure, or privilege escalation primitive is demonstrated by the patch. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES BPF SIMPLEFIX LINUS YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap was applied. 2. Signal breakdown * +1 Reliable kernel stall or DoS concern. The verifier can permit a helper that may block on filesystem reads from explicit RCU, preemption-disabled, or timer-callback contexts. Blocking in such contexts can produce sleep-in-atomic warnings, lockups, or stalled execution. * +0 No concrete memory-corruption primitive. The patch only adds might_sleep metadata to BPF helper prototypes. * +0 No UAF, stale reference, refcount misuse, OOB access, arbitrary write, or controlled reclaim is established. * +0 No confidentiality or integrity impact is established. * +0 Remote reachability is not established. This is a local BPF program verifier and execution-context issue. * +0 Local unprivileged trigger is not awarded. The supplied evidence does not establish that the complete BPF load, attach, and trigger sequence is usable by an ordinary unprivileged user. * No privilege penalty is applied. Host-admin-equivalent privilege is not positively established, but below-host-admin reachability is also not established. * No hard-race penalty is applied. The defect is an incorrect verifier context classification, not a timing race. * No BPF structured-object leverage is awarded. The issue does not involve a stale BPF object, controlled reuse, or post-free field consumption. * No additional Availability point is awarded. The possible lockup is the same demonstrated availability consequence. 3. Reachability analysis The trigger requires loading a BPF program that uses the faultable variants of bpf_get_stack or bpf_get_task_stack and arranging execution from a non-sleepable region within an otherwise sleepable program. Relevant examples include an explicit RCU region, a preemption-disabled region, or a non-sleepable timer callback. The complete privilege boundary is unresolved from the supplied patch. BPF loading and attachment are commonly gated by CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN, or product-specific BPF policy. The patch does not establish that all required stages can be performed by an ordinary user, a container user, or an attacker with only namespace-scoped capabilities. Namespace-scoped privilege is therefore UNKNOWN. A network namespace, container, or delegated BPF capability alone would not prove that program loading, attachment, callback setup, and triggering all work below host-admin-equivalent privilege. No special hardware, boot option, or firmware condition is indicated. 4. Primitive and severity interpretation The exact primitive is an invalid execution-context transition. A BPF helper that may fault and block on filesystem reads was incorrectly represented to the verifier as non-sleepable. This can permit the helper in contexts where sleeping is unsafe. This is not a memory lifetime defect. There is no active structured stale object, fixed stale storage, UAF, double release, refcount mutation, arbitrary write, disclosure path, authorization bypass, or privilege-escalation primitive in the supplied evidence. The demonstrated consequence is limited to possible sleep-in-atomic warnings, lockups, or denial of service. A kernel crash is plausible in configurations that treat such invalid execution as fatal, but it is not directly demonstrated by the patch. Stronger outcomes such as code execution, confidentiality loss, integrity loss, or privilege escalation are speculative and are not scored. PrimitiveClass is CLASS_C because the established behavior is invalid-state and availability-oriented rather than corruption-oriented. ImportantCandidate is NO because no meaningful unresolved exploitation primitive exists beyond the potential stall or DoS. AutoDowngradeAllowed is YES because the issue is not supported by a concrete corruption, ownership, authorization, or security-boundary primitive. 5. One-sentence report phrase A BPF verifier context-validation flaw can allow faultable stack helpers to block in non-sleepable RCU, preemption-disabled, or timer callback contexts, potentially causing a kernel lockup or denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review the evaluated product BPF policy to determine whether a below-host-admin actor can load, attach, and execute the required sleepable BPF program path. The supplied patch itself supports availability impact only and does not establish memory corruption or privilege escalation. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Mark faultable stack helpers as sleepable [ Upstream Commit: 44b8d370f2725bad215da3e67668e98ba96671bd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44b8d370f2725bad215da3e67668e98ba96671bd Changed files: kernel/bpf/stackmap.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44b8d370f2725bad215da3e67668e98ba96671bd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98045 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98045 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: Not available The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: unknown Paranoid ActionableScore: 1 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).